The aim of the present invention is to provide a system from a horizontal deviation of a load receiving element in relation to a position of a hoist travelling trolley, wherein the load receiving element being suspendedly arranged on a plurality of supporting cables on the hoist travelling trolley, as well as a method for measuring a horizontal deflection of a load receiving element in relation to a position of a hoist travelling trolley, wherein the load receiving element being suspendedly arranged on a plurality of supporting cables on the hoist travelling trolley.
During the transportation of loads by bridge crane or gantry crane, ship unloader, girder bridge cranes, as well as coil and steel store gantry cranes, loads are regularly lifted from a location A at a level of h0 to a transport level of h1, whereupon they are transported to a destination B at a height of h2 by a predetermined and normally time-optimized route.
In the case of all afore mentioned means of transport, a so-called hoist travelling trolley is provided on a cross beam on which, connected by supporting cables, load receiving elements such as gripping devices for receiving loads, for example containers, pallets and the like are arranged.
After receiving the load at location A, a horizontal movement of the hoist travelling trolley is regularly effected, wherein, due to the inertia, the loads suspended from the cables are accelerated or respectively decelerated in relation to the hoist travelling trolley in a delayed fashion. These acceleration or deceleration processes lead to a horizontal deviation of the load receiving element in relation to the position of the hoist traveling trolley. This deviation occurs regularly during transportation of the loads suspended from the supporting cables, with the consequence that an undesirable oscillation of the loads attached to the supporting cables will be initiated during a steady movement of the hoist traveling trolley.
One of the constant tasks of a crane operator, therefore, is to counteract these oscillatory movements. A practised and attentive crane operator will achieve this through skillful countersteering during the transport movement. If, however, the operator is unpractised or unattentive, the transportation operations and handling times may be considerably extended. In the worst case, there will be a higher risk of collisions and accidents.
There are known oscillation damping devices by CePLuS in Magdeburg which use high-performance cameras with microprocessors for measuring a horizontal deviation of the load receiving element. These high-performance cameras are mounted to a hoist travelling trolley and measure the movements of the loads so they can adapt the velocity of the hoist travelling trolley while traversing in order to prevent undesirable oscillation of the loads from occurring.
Reflectors are attached to the load receiving element in order to measure the deviation of the load receiving element. The camera mounted on the hoist travelling trolley is directed downwards, i.e. in the direction of the load receiving element, and determines the position of the reflector relative to the hoist travelling trolley. The deviation of the load receiving element is computed from this position data for the reflector.
A drawback of the CeSAR system by CePLuS has been that the time intervals for determining the deviation are too large for realtime dynamic control, and further, the resolution with regard to the accuracy of measurement of the camera measurement system is insufficient to meet the demands of the realtime dynamic control. In addition to this detrimental system data, the overall size of the CeSAR oscillation damping system has proved to be disadvantageous, since the reflectors which must be attached to the load receiving element have unfavourable dimensions. A further drawback of the CeSAR system is the limited field of view if at least a certain degree of measurement accuracy is required to be achieved, as the accuracy of measurement of the camera lens correlates to the horizontal field angle. A large horizontal field angle requires, therefore, a so-called wide angle lens which, however, is detrimental to image resolution and, ultimately, accuracy of measurement.
One more drawback of the CeSAR system is the frequency of maintenance required by the optical devices. This is because during usage in conventional storage environments, a certain degree of contamination of the racks, goods to be and, consequently, the means of transport is to be expected at regular intervals, with the result that the optical devices, such as the camera lens, will have to be cleaned frequently.